1. Field of the Invention
The present invention relates to a control negative for use in setting a photo-printer to proper exposure conditions, prior to actual printing. More particularly, the present invention relates to a control negative which enables setting up proper exposure conditions in any kind of photo-printer without measuring three color densities of a sample print made from the control negative.
2. Background Art
An automatic photo-printer determines an appropriate print-exposure in accordance with three color densities of a negative to be printed, which are measured by an image scanner such as a CCD scanner mounted in the photo-printer. To achieve a homogeneous image quality, the exposure conditions in the photo-printer are checked prior to the practical printing to set up proper exposure conditions. This is because the exposure conditions can change according to the photo-printer type or changes in properties of the same photo-printer, or according to a difference in color characteristics among color papers or lenses used for printing.
For setting up proper exposure conditions for three colors in the photo-printer, first a sample print is made from a specific control negative (or called a set-up negative), without effecting any exposure correction to the photo-printer. Next, densities of three colors, such as yellow, magenta and cyan, of the sample print are measured by a density measurement device. Then, three color densities of a previously provided reference print made from the control negative under optimum exposure conditions in the factory or the photofinisher, are also measured by the density measurement device to detect a difference in density between the sample print and the reference print, color by color.
Generally, most original frames expected to be printed have been photographed under daylight, i.e., sunlight from 10 a.m. to 2 p.m., or under similar exposure conditions, at proper exposure values determined based on the film speed, so that most negatives have proper image densities. In addition, it is usual that a human subject occupies about one-third of the entire area of each negative frame, while the remaining area, i.e. the background is occupied by landscapes such as trees, sky, walls and so forth. In principle, mixture of three color transmittance densities of all pixels of a properly exposed negative results in a neutral gray.
Therefore, as a representative of ordinary negatives, conventional control negative kit 2 contains a round eye portion 3 in a center of the frame, wherein mixture of light bundles transmitting through the round eye portion 3 represent a neutral gray. A background 4 of a different color density surrounds the eye portion 3, as is shown in FIG. 13. Control negative frames 5 to 8 are photographed from the same original at different exposure values. The frame 5 is photographed at a normal exposure value, so is called a normal exposed frame. The frame 6 is photographed at an insufficient exposure value, so is called an under-exposed frame. The frame 7 is photographed at an excessive exposure value, so is called an over-exposed frame. The frame 8 is photographed at a greatly excessive exposure value, so is called a super over-exposed frame. The normal exposed frame 5 represents a standard original frame to be printed. Besides these control negative frames 5 to 8, there is provided a blank frame 9 with no image on the control negative kit 2 to show a basic density of the filmstrip used for the control negative kit 2.
According to the difference in three color densities between the sample print and the reference print, an exposure correction value is determined for any one of the three colors, and is entered through correction keys. In this way, the photo-printer is set to proper exposure conditions where a print made from the control negative would have the same density and color balance as the reference print. The density measurement device is usually incorporated in the photo-printer, to measure three color densities from a predetermined central area of the sample print or the reference print.
Thus, the conventional control negative with the center eye portion needs density measurement of the sample print, and is therefore inconvenient and inefficient.
It is also known to use a control negative which has a pictorial full-color image such as a portrait in place of the center eye portion, in order to enable the operation to determine with the naked eye if color balance and density of the sample print are proper or not.
However, it has been difficult to make an accurate determination based on the visual inspection of the pictorial image on the sample print made from the conventional control negative.